Year Percent 1985-01-01 21.8395000000000000 1986-01-01 23.5357000000000000 1987-01-01 21.5340000000000020 1988-01-01 20.1498000000000000 1989-01-01 25.8991000000000000 1990-01-01 25.8023000000000000 1991-01-01 28.9670000000000000 1992-01-01 25.4751000000000000 1993-01-01 13.6038000000000000 1994-01-01 4.5364400000000000 1995-01-01 4.5134300000000005 1996-01-01 4.2553300000000010 1997-01-01 3.6249500000000000 1998-01-01 6.0363100000000000 1999-01-01 4.1479700000000000 2000-01-01 3.1120400000000004 2001-01-01 2.7048900000000002 2002-01-01 3.2844200000000000 2003-01-01 2.5808000000000000 2004-01-01 1.9303099999999997 2005-01-01 1.9358799999999998 2006-01-01 2.2198400000000000 2007-01-01 2.5639500000000000 2008-01-01 3.2787200000000000 2009-01-01 5.7149900000000000 2010-01-01 6.1897000000000000 2011-01-01 6.5126300000000010 2012-01-01 6.0121900000000000 2013-01-01 6.7263800000000010 2014-01-01 8.6466700000000000 2015-01-01 14.8261000000000000 2016-01-01 19.6550000000000000